For example, for a hybrid vehicle, instead of a conventional brake system, which operates a brake through a hydraulic pressure, adopted is a brake system of a by-wire type that operates a brake through an electrical signal. Such a brake system of a by-wire type is provided with a stroke simulator that creates a pseudo reaction force corresponding to an operation amount of a brake pedal so as not to make the operation feeling of the brake pedal different from that of a conventional brake system (for example, see Patent Literature 1).
As an example of such a stroke simulator, the present applicant of the present application has presented a stroke simulator configured by disposing, serially to each other, a first elastic member having a first elastic modulus and a second elastic member having a second elastic modulus larger than the first elastic modulus (for example, see Patent Literature 2).
By the stroke simulator according to Patent Literature 2, regarding reaction force characteristic against the operation amount of a brake, it is possible to create an appropriate reaction force corresponding to the operation amount of the brake such as to create a small reaction in case the operation amount is small and a large reaction force in case the operation amount is large.